1. Field
Various embodiments of the present invention relate to an electronic apparatus, and more particularly, to a counting apparatus using a digital double sampling (DDS) scheme based on global counting, and an image sensor including the same.
2. Description of the Related Art
Electronic apparatuses use counters to convert measurements such as intensity of light, intensity of sound, and time into digital signals.
For example, an image sensor acquires an image by using semiconductor properties that respond to incident light, and includes analog-to-digital converters to convert an analog signal outputted from a pixel array into a digital signal. The analog-to-digital converters (ADC) have counters that perform counting operations based on a clock. That is, a single slope analog-to-digital converter (i.e., a single slope ADC) in an image sensor uses a counter to convert a signal into a digital code according to a pulse width of the signal.
Performance of systems that have counters is directly influenced by the operation speed and power consumption of the counters. This includes image sensors because they generally have multiple counters to convert analog signals outputted from a pixel array into digital signals. The number of counters increases as the resolution of image sensors increases. As the number of counters increases, the operation speed and power consumption of the counters becomes an even more important factor in determining overall performance.
In a global counting structure, a digital double sampling (DDS) scheme is used to cancel readout offset. Therefore, a line memory for counting readout offsets and a line memory for counting pixel signal's are used, resulting in an increase in memory capacity.